To increase our knowledge of newborn surgical physiology and improve clinical management by studying the metabolic and hemodynamic responses of the newborn organism to life threatening challenges. Work in Progress: Goal - to determine the metabolic and hemodynamic characteristics of the normal newborn and maturing pig. We have completed 150 experiments and plan to study a total of 200 animals. The following variables are measured: hemoglobin, hematocrit, serum sodium, potassium, chloride, BUN, osmolality, total protein and colloid oncotic pressure; urine specific gravity, osmolality, sodium and potassium; pulse rate, cardiac index, total peripheral resistence, arterial blood pressure and respiratory rate. A second study almost completed is the hemodynamic and metabolic responses of the neonatal piglet to pharmacologic doses of methylprednisolone. Twenty piglets 1 - 4 days of age were studied. Group 1 animals had an intravenous bolus injection of 30 micrograms/kg of methylprednisolone and Group 2 animals a similar volume of sodium chloride solution. Serial measurements were made of the occurrence of right to left shunts, pulse rate, total peripheral resistance, blood pressure, cardiac index, serum osmolality, serum sodium and potassium, total protein, colloid oncotic pressure, urine volume, urine osmolality, sodium and potassium. Our third future project pilot studies have been completed on an experimental preparation to test the efficacy of various intravenous solutions containing colloid and non-colloid in closed loop intestinal obstruction. This experiment involves the creation of an isolated loop of terminal ileum and measurements of the water content and electrolyte content of the bowel loop following infusions of various electrolyte solutions.